In the Middle Ages Nowy Jasiniec castle served as a border stronghold on the trade route from Polish to Pomesania. It was conquered and rebuilt by the Teutonic Order in the 14h century. During the wars between Teutonic Order and Poland it was destroyed and then rebuilt again in 1454. Between 1466-1772 Nowy Jasiniec was the seat of local lords. Between 1773-1846 the castle served as an evangelical church. Later it fell into disrepair and is today in ruins.
The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.